Cardiac arrest is a life-threatening medical condition in which the patient's heart fails to provide blood flow to support life. A defibrillator can be used to deliver defibrillating shocks to a patient suffering from cardiac arrest. The defibrillator resolves this condition by delivering a high-voltage impulse to the heart in order to restore normal rhythm and contractile function in patients who are experiencing arrhythmia such as VF (ventricular fibrillation) or VT (ventricular tachycardia) that is not accompanied by spontaneous circulation. One type of defibrillator, the automated external defibrillator (AED), differs from manual defibrillators in that the AED can automatically analyze the electrocardiogram (ECG) rhythm to determine if defibrillation is necessary. The defibrillator analyzes the ECG signal for signs of arrhythmia. If VF is detected, the defibrillator signals the rescuer that a shock is advised. After the detection of VF or other shockable rhythm, the rescuer presses a shock button on the defibrillator to deliver a defibrillation pulse to resuscitate the patient.
Defibrillation must be delivered very soon after the onset of cardiac arrest in order to be effective. It is estimated that the chance of survival falls by 10% for every minute of delay to defibrillation beyond four minutes after cardiac arrest. Hence, AEDs are designed to be used by first responders, such as firefighters, police, or lay bystanders, who are the most likely to arrive at the patient's side first. Once an AED is brought to the patient, the rescuer must deploy and use it quickly.
Some prior art defibrillators are designed to power on automatically when the defibrillator carry case is opened in order to minimize the time until the AED is ready to delivery therapy. For example, U.S. Pat. No. 6,083,246, entitled “Lid open detection circuit for automated external defibrillators” by Stendahl et al. describes an AED which automatically activates when a lid is opened to deploy the electrodes inside. Another co-assigned application, PCT/IB2011/054822 entitled “CARRYING CASE WITH IMPROVED ACCESS FOR DEFIBRILLATOR AND ACCESSORIES” by Roach et al. and herein incorporated by reference, describes a defibrillator system in which a carrying case has a lid open sensor for automatically activating the defibrillator inside when the case is opened.
AEDs often include electrodes and other accessories which aid in the administration of cardiopulmonary resuscitation (CPR) during the rescue. FIG. 1 illustrates one defibrillator carrying case, in which a set of patient electrodes 140 and a fast response kit 130 are stored within the case with the AED itself.
Such prior art defibrillators are portable and battery powered. Each time that the defibrillator is automatically activated by opening the lid, the battery suffers some depletion. It is important then that the automatic activation is intended for some purpose. Otherwise, the defibrillator battery is unnecessarily depleted, which costs money and potentially delays therapy while the depleted battery is changed out.
Inadvertent activation of the defibrillator can occur for a variety of reasons. The carry case latch may fail in a way that is not readily observable by the owner. The automatic power on sensor may malfunction and issue spurious activation indications to the device. More commonly, the carry case becomes overstuffed with accessories, which causes the case to become distorted such that the case opening sensor activates. Any of these problems would cause the automatic power on feature to unnecessarily activate the defibrillator and deplete the battery. What is needed then is a solution to this problem.